The invention relates to methods and compositions for inhibiting corrosion of metals, and, in one aspect, more particularly relates to methods and compositions for inhibiting corrosion of metals in acid environments where the acid contains halogen, such as hydrochloric acid, hydrofluoric acid, and the like.
It is well known that steel surfaces will corrode in the presence of acid environments. While the rate at which corrosion will occur depends on a number of factors, such as the steel alloy itself, the strength and type of acid, the temperature of the environment, the length of contact, etc., some sort of corrosion invariably occurs. Alloy technology has provided materials to withstand the incidental contact of steel with add, but the corrosion problem is particularly aggravated when there is no choice but to contact steel with acid, as in the case of chemical processing where acids are employed. In instances where acid is not required to remain pure and where the contact is inevitable, attention has turned toward providing corrosion inhibitors in the acid medium itself to prevent corrosion of the steel surfaces that it must come into contact with, yet still deliver the acid to its ultimate destination. It would be advantageous if a new corrosion inhibitor were discovered that would be an improvement over the presently known systems. For example, a corrosion inhibitor providing a large corrosion inhibiting effect for a small proportion used would be advantageous.
A specific environment in which an improved corrosion inhibitor would be appreciated is in the oil patch. It is well known that during the production life of an oil or gas well, the production zone within the well may be chemically treated or otherwise stimulated to enhance the economical production lifetime of the well. A common way of doing this is by acid fracturing or matrix acidizing, whereby a highly acidic solution, generally having a pH of less than about 1, but which may be as high as about 6.9 is injected into the well. Spent acid in return fluids may have a pH of around 3-6.9, and organic acids used in acidizing include formic acid and acetic acid, each of which have a pH below 6.9. Because of the acidic nature of the treatment fluid, the production or workover conduit which is utilized in the well in such applications encounters considerable acidic corrosion, in the forms of surface pitting, embrittlement, loss of metal component and the like.
In earlier years of producing subterranean wells, the vast majority of production and workover conduits comprised carbon steels; they were utilized either temporarily or permanently in the well, and treatment and/or stimulation fluids were introduced through them into the well. Recently, due primarily to the drilling and completion of many subterranean wells through formations which contain high concentrations of corrosive fluids such as hydrogen sulfide, carbon dioxide, brine, and combinations of these constituents, the production and workover conduits for use in the wells have been made of high alloy steels. The high alloy steels include chrome steels, duplex steels, stainless steels, martensitic alloy steels, ferritic alloy steels, austenitic stainless steels, precipitation-hardened stainless steels, high nickel content steels, and the like.
Corrosion inhibitors containing iodine and other halogens are known. For example, U.S. Pat. No. 2,989,568 relates to the preparation of halogenated acetylenic alcohols containing chlorine or bromine. Such compounds are described as useful as corrosion stabilizers for chlorinated solvents such as trichloroethylene and as inhibitors in plating baths.
The effects of inorganic anions, organic compounds, and combinations of the two on corrosion of mild steel in various acids were determined by N. Hackerman, et al. as described in xe2x80x9cEffects of Anions on Corrosion Inhibition by Organic Compounds,xe2x80x9d Journal of the Electrochemical Society, Vol. 113, No. 7, July 1966, pp. 677-81. From corrosion rates of steel in adds, the order of the degree of adsorption of anions was concluded to be: Ixe2x88x92 greater than Brxe2x88x92 greater than Clxe2x88x92 greater than SO4= greater than ClO4xe2x88x92.
U.S. Pat. No. 3,686,129 mentions that hydrogen embrittlement which normally occurs when high strength metal parts are immersed in acid-cleaning solution, is minimized or eliminated by adding certain combinations of (1) mono-alkynols and (2) iodine compounds which are either iodo-alkenols or suppliers of iodide ion.
Inhibited treating acids for use in contact with ferrous surfaces at temperatures of from about 150xc2x0 F. to about 450xc2x0 F. are described in U.S. Pat. No. 3,773,465. Cuprous iodide is present in a concentration of from about 25 ppm to about 25,000 ppm by weight of the treating acid.
U.S. Pat. No. 3,816,322 describes that iron surfaces are protected against corrosion by aqueous acidic solutions containing a polyhydric compound or derivative thereof by dispersing into the corrosive solution which will contact the metal surface an effective amount of a heterocyclic amine, an acetylenic alcohol, and an ionizable iodine containing compound.
There remains a need for new, stable corrosion inhibitors and methods therefor which would work in halogen acid environments for a wide variety of steels. For example, iodine alone formulated with conventional corrosion inhibitor ingredients can enhance halogen acid corrosion control primarily of chrome steels, but also carbon steels. However, with time, iodine corrosion inhibitors tend to become less effective. In one non-limiting theory, it is believed that the iodine slowly reacts with organic materials, or at least the organic materials are the cause for formulation degradation.
Accordingly, it is an object of the present invention to provide compositions of matter effective in the inhibition of corrosion in halogen acid environments.
It is another object of the present invention to provide compositions for minimizing corrosion in halogen acid situations, which compositions may be easily made.
It is yet another object of the invention to provide methods and compositions for suppressing the corrosion of steels in halogen acid environments which can be readily implemented using conventional equipment.
Still another object of the invention is to provide an iodine-containing halogen acid corrosion inhibitor which is stable over time.
In carrying out these and other objects of the invention, there is provided, in one form, a method for inhibiting the corrosion of metals in contact with an acidic liquid medium which involves providing a liquid medium containing an acid, and then adding to the liquid medium an effective amount of a corrosion inhibitor comprising a reaction product of iodine and propargyl alcohol. Other ingredients may be added, of course.
It has been discovered that the reaction product of iodine in an excess of pargyl alcohol gives compound (I): 
That is, 2,3di-iodo-2-propen-1-ol in propargyl alcohol. The resulting product is propargyl alcohol white and it is acid soluble. As will be shown, it is a useful ingredient used to prepare a halogen acid corrosion inhibitors, and mixed halogen acid/organic acid corrosion inhibitors, such as combinations of acetic acid and HF, and/or formic acid/HF. The halogen acid environments where the invention is useful encompass acid environments where the acid includes, but is not limited to, hydrochloric acid, hydrofluoric acid, formic acid, acetic acid, and mixtures thereof. Intermediate compound (I) has been found to have excellent stability, thus avoiding degradation over time. Compound (I) is an intermediate which is used in an inhibitor composition.
In one preferred embodiment of the invention the intermediate corrosion inhibitor (I) is made by reacting from about 6 parts by weight of propargyl alcohol to about 1 part by weight of iodine. In a broad range, the weight ratio range of propargyl alcohol to iodine is from about 1.1:1 to about 12:1. In a preferred embodiment of the invention, the weight ratio range of propargyl alcohol to iodine is from about 6:1 to about 4:1.5. It will be appreciated that the iodine reactant is relatively expensive, and it is thus desirable to minimize its proportion. The temperature for this reaction may range from about ambient to 140xc2x0 C. No catalyst is required.
The acid corrosion inhibitor intermediate to be combined with the acidic injection medium and the intensifier can be any acetylenic compound such as acetylenic alcohol; a nitrogen compound, such as a quaternary ammonium compound; and aromatic hydrocarbon or mixtures thereof, as is known to those skilled in the art. For example, acid corrosion inhibitors as made and described in U.S. Pat. Nos. 3,514,410; 3,404,094; 3,107,221; 2,993,863; and 3,382,179; may be utilized in accordance with the present invention.
Examples of acetylenic compounds which may be used include hexynol, dimethyl hexynol, diethyl hexynediol, dimethyl hexynediol, dimethyl octynediol, methyl butynol, methyl pentynol, ethynyl cyclohexynol, 2-ethyl hexynol, phenyl butynol, and ditertiary acetylenic glycol.
Other acetylenic compounds which can be employed in accordance with the present invention include, but are not limited to, butynediol; 1-ethynyl-cyclohexanol; 3-methyl-1-nonyn-3ol; 2-methyl-3-butyn-2-ol; also 1-propyn-3ol; 1-butyn-3-ol; 1-pentyn-3-ol; 1-heptyn-3-ol; 1-octyn-3-ol; 1-nonyn-3-ol; 1-decyn-3-ol; 1-(2,4,6-trimethyl-3-cyclohexenyl)-3-propyne-1-ol; and in general acetylenic compounds having the general formula: 
wherein R1 is xe2x80x94H, xe2x80x94OH, or an alkyl radical; R2 is xe2x80x94H, or an alkyl, phenyl, substituted phenyl or hydroxyalkyl radical; and R3is xe2x80x94H or an alkyl, phenyl, substituted phenyl or hydroxyalkyl radical.
Acetylenic sulfides having the general formula:
HCxe2x89xa1Cxe2x80x94Rxe2x80x94Sxe2x80x94Rxe2x80x94Cxe2x89xa1CH
can also be employed in the present invention in lieu of acetylenic alcohols. Examples of these are dipropargyl sulfide, bis-(1-methyl-2-propynyl)sulfide and bis-(2-ethynyl-2-propyl)sulfide.
The nitrogen or ammonia compounds can be optionally employed in accordance with the present invention, and they may include, but are not limited to, those amines having from 1 to twenty-four carbon atoms in each alkyl moiety as well as the six-membered heterocyclic amines, for example, alkyl pyridines, crude quinolines and mixtures thereof. This includes such amines as ethylamine, diethylamine, triethylamine, propylamine, dipropyl-amine, tripropylamine, mono-, di- and tripentylamine, mono-, di- and trihexylamine and isomers of these such as isopropylamine, tertiary-butylamine, etc. This also includes alkyl pyridines having from one to five nuclear alkyl substituents per pyridine moiety, such alkyl substituents having from one to 12 carbon atoms, and preferably those having an average of six carbon atoms per pyridine moiety, such as a mixture of high boiling tertiary-nitrogen-heterocyclic compounds, such as HAP (high alkyl pyridines), Reilly 10-20 base and alkyl pyridines H3. Other nitrogen compounds include the crude quinolines having a variety of substituents.
The inhibitor may also contain a number of other constituents, such as nonyl phenol adducts and tallow amine adducts, tall oil adducts, such as surfactants. Components such as heavy aromatic solvents and fatty acids, may also be present as oils for oil wetting. Surfactants also aid in oil wetting.
A necessary component of the treatment fluid of the present invention is the iodine/propargyl alcohol reaction product (I), previously described. The proportion of the reaction product is in excess of propargyl alcohol present per se. The overall corrosion inhibitor formulation may contain from about 1 to about 100 pbw or wt. % iodine/propargyl alcohol reaction product (I), preferably from about 2 to about 25 pbw or wt. %, and most preferably from about 3 to about 10 pbw or wt. %.
It will be appreciated that the halogen acid corrosion inhibitor of this invention may be used with conventional corrosion inhibitors such as those described below, in any application where a steel surface, such as stainless steel, high alloy or other steel, is exposed to an acid environment. While the specific implementation of this invention is described in the context of the oil patch, the invention may certainly find uses in other applications where it is desirable to reduce corrosion, such as chemical processes that necessarily require the contact of acids with conduits, fittings, and other equipment.
In the implementation of the invention in the production of fluids from subterranean reservoirs, a fluid is introduced through a high alloy steel member or conduit positioned within the well. The fluid is an acidic injection medium and includes an acid corrosion inhibitor. The invention also encompasses a method of treating a well for enhancement of production within a production zone by introduction into the steel conduit of the acid corrosion inhibitor composition of this invention.
The fluid which is contemplated for use in one aspect of the present invention for treatment of a subterranean well for enhancement of production will be aqueous based; that is, it will be formed using sea water available at the well location, a brine, tap water or similar fluid. The amount of fluid used for the treatment will vary, of course, from well to well, and will be based upon the particular application at hand, and the amount thereof is not particularly critical to the method of the present invention. It will be appreciated that one of ordinary skill in the art of corrosion inhibition will be able to adapt the teachings of this invention to applications outside the realm of oil and gas recovery, such as the area of chemical processing, with only routine experimentation.
The expected treatment fluid in an oil production environment is expected to have as a primary additive an acidic injection medium which may be any compatible acid, including but not limited to hydrochloric acid, hydrofluoric acid, formic acid, acetic acid, and mixtures thereof. The fluid with the acid injection medium therein should have a pH of no greater than about 6.9. Acidizing fluids have pH of less than 1 when mixed with produced fluids which may have a pH as high as 6.9.
The treatment fluid also contemplates incorporation of other acid corrosion inhibitors which typically will be provided in treatment concentrations of from about 1,000 ppm, based upon the weight of the entire treatment fluid to about 60,000 ppm of such weight. Most often, the total amount of corrosion inhibitors will range from about 1,000 to 20,000 ppm including any intensifier, if present. Formic acid is an intensifier and can be used at concentrations up to 100,000 ppm or more. Again, the treatment level of the acid corrosion inhibitor will vary depending upon the particular physical characteristics of the well, the high alloy steel conduit, temperature and pressure considerations, the selected acidic injection medium, and the like.
It will be appreciated that the treatment level of the acid corrosion inhibitor of this invention will vary depending upon a wide variety of parameters including, but not limited to, the particular physical characteristics of the system or well, the nature of the steel, temperature and pressure considerations, the acid and strength thereof in the system, and the like. Nevertheless, to give a sense of the typical proportions that might be used, non-limiting effective amounts of reaction product in the corrosion inhibitor ranges from about 1 to about 20 gpt (gallons of inhibitor per thousand gallons of acid), depending on the acid strength. The treatment level also depends upon the temperature and exposure time, with the following being non-limiting, representative examples:
1-3 gpt at ambient to 200xc2x0 F. in 15% HCl and 6 hours exposure;
1-5 gpt at ambient to 200xc2x0 F. in 28% HCl and 6 hours exposure;
3-10 gpt at 200 to 250xc2x0 F. in 15% HCl and 6 hours exposure; and
5-15 gpt at 200 to 250xc2x0 F. in 28% HCl and 6 hours exposure.
Twenty (20) gpt of corrosion inhibitor plus intensifiers is commonly used in acid systems at or above 250xc2x0 F. Intensifiers are ingredients that extend inhibition of the inhibitor. Common intensifiers include, but are not necessarily limited to Cu2I2, KI, formic acid, and the like. Intensifiers are not corrosion inhibitors themselves.
The invention will be described further in the following illustrative Examples, which are non-limiting and serve only to further teach the invention.